Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$46.55	11.321%	$51.8199	$51.82	$51.80	$51.80
Purchase #2	$20.27	5.433%	$21.3713	$21.37	$21.35	$21.40
Purchase #3	$95.54	8.159%	$103.3351	$103.34	$103.35	$103.30
Purchase #4	$42.26	9.160%	$46.131	$46.13	$46.15	$46.10
Purchase #5	$58.82	7.685%	$63.3403	$63.34	$63.35	$63.30
Purchase #6	$208.88	10.388%	$230.5785	$230.58	$230.60	$230.60
Purchase #7	$167.73	13.705%	$190.7174	$190.72	$190.70	$190.70
7 purchase totals =	$640.05		$707.2935	$707.30	$707.30	$707.20